At present LED lamps have been widely used in street lighting, as usually lighting streets requires high illumination brightness, wide illumination angles and long illumination distances, in order to satisfy these conditions, a plurality of LED chips connected all together are used in a single LED street lamp, thus, the size and weight of the whole device are increased. At the same time these LED chips will generate a great deal of heat in operating, requiring a corresponding heat dissipation device which requires lots of open space as well. Furthermore, as the conventional heat dissipation devices used in LED street lamps are usually heat sinks made of metal materials, more heat dissipating capacity provided means larger size and greater weight. Under these circumstances, the lamp holder must be redesigned to conform to the overweighed lamp. However, for the common lamp holders, for example, E40, its maximum load has been limited by its structure, if the weight of the lamp exceeds the maximum load of the holder, the connection may come unstable, the lamp may fall down from the holder, and the holder may be damaged.
Recently some relevant products in the market have been redesigned, for example in U.S. patent 2006/0067076A1, the supporting structure of the LED street lamp is enhanced to some extent, but these products still cannot fully satisfy the requirements of the LED street lamps with increasing weight and size.